Line-scan laser ophthalmoscope

ABSTRACT

Systems and methods for providing a line-scanning laser ophthalmoscope (LSLO) are disclosed. The LSLO uses a substantially point source of light, such as an infrared laser or a super-luminescent diode. The point source is expanded to a line. The LSLO scans the line of light in a direction perpendicular to the line across a region of an eye having an undilated pupil The reflected light is received confocally, using monostatic beam geometry. A beam separator, such as a turning prism or mirror, diverts one of the incoming light and the reflected light to separate the light. An optical stop prevents non-confocally received light from reaching a one-dimensional detector, such as a linear CCD array. An electrical signal responsive to the output light at each of a plurality of locations along the line of output light is processed to provide images of the scanned portion of the eye.

GOVERNMENT RIGHTS

This invention was made with government support under Contract No. 1 R43EY 11819-01A1 awarded by the National Institutes of Health/National EyeInstitute. The government may have certain rights in the invention.

FIELD OF THE INVENTION

This invention relates generally to systems and methods for examiningeyes. More particularly, the invention relates to systems and methodsthat employ scanned lines of light for examining eyes.

BACKGROUND OF THE INVENTION

Fundus imaging is the essential diagnostic procedure in ophthalmology.Instruments of the prior art that are useful for examining the fundus ofthe eye include direct and indirect ophthalmoscopes, the slit-lampbiomicroscope and the fundus camera. Complementary tools have beendeveloped that broaden diagnostic and therapeutic possibilities, such asthe Scanning Laser Ophthalmoscope (SLO). The SLO is a superior tool forrapidly and continuously acquiring high-contrast images of the ocularfundus and its structures, including the distribution of choroidalblood, melanin, and retinal pigments. Because it accommodates a varietyof visible and NIR wavelengths, the SLO is especially useful for thestudy and early diagnosis of diseases such as age-related maculardegeneration (AMD) and diabetic retinopathy. These are the leadingcauses of blindness in the elderly. The SLO is a powerful diagnostictool for characterizing retinal pathologies, as well as for angiography,tomography, perimetry, and general psychophysics. Confocal SLO imagingis very effective in patients suffering from mild cataract, or frompathologies causing clouding of the vitreous. Another device forexamining the fundus of the eye is the instrument described in U.S. Pat.No. 6,267,477, issued on Jul. 31, 2001 to Karpol et al. The Karpolinstrument is described as operating on the principle of slit lampbimicroscopy performed on an eye having a dilated pupil. The Karpolinstrument uses a defined angle between a beam going to the retina and abeam returning from the retina, and there is a distance at the area ofthe pupil between the incident beam and the measured scattered beams.The Karpol instrument uses a two dimensional CCD camera as one of threecameras used to record images.

However, although they have become valuable diagnostic tools in theresearch community, scanning laser devices have not yet emerged intowidespread clinical usage, due in part to their size, cost, andcomplexity. As a result, they are usually found only at specializedfacilities, are used almost exclusively by ophthalmologists, and areoften unavailable when needed. In particular, elderly and emergencypatients are often unwilling or unable to travel to a specialized clinicfor testing. But even the ubiquity of slit-lamps, fundus cameras andindirect ophthalmoscopes does not necessarily allow their use in manycircumstances in which they may be indicated, such as emergency care.These devices may not be immediately accessible, and in manycircumstances, the primary care physician may not choose to useinstruments like Binocular Indirect Ophthalmoscopes (BIO's) which aremore difficult to master, and may be unpleasant for the patient. Thefallback device is the direct ophthalmoscope. The availability ofhand-held and tele-ophthalmoscopic fundus imaging systems of thestandard types are increasing, but their cost remains high, and theycontinue to have the limitations discussed. A portable, convenient, andless expensive system that provides high quality images of the fundushas been lacking.

SUMMARY OF THE INVENTION

The line-scanning laser ophthalmoscope (LSLO) of the invention has asignificant confocal advantage in image clarity and contrast, and depthof penetration at the ocular fundus compared with conventional digitalfundus photography. The LSLO has features not currently available incommercial SLOs, and is less expensive. The hand-held digital LSLO hasproven that high quality, non-mydriatic (e.g., undilated pupil),line-confocal retinal images and stereo pairs can be obtained with asimple, compact design with fewer moving parts and components thancurrent SLO systems. In one embodiment, the system and method involves amonostatic beam geometry, e.g., the light incoming to the thing to beobserved, and the light collected in reflection from the thing, passthrough the same location in space between the thing and the opticalcomponent nearest the thing. As a result of the monostatic beamgeometry, the instrument can be operated with a small, undilated pupil.The instrument remains operative even if the pupil is dilated, however.

There are many benefits that accrue if the pupil of an eye is notrequired to be dilated for the systems and methods of the invention tofunction correctly. Dilation is generally performed by applyingchemicals topically and waiting for the dilation to occur. The waitingperiod can be some minutes, typically twenty minutes. Absence of adilation requirement means that an instrument embodying principles ofthe invention can be used immediately, rather than only after a delaynecessitated by the dilation of the pupil. This allows use in settingssuch as emergency or field use, where other instruments become usefulonly after the dilation of the pupil is complete. Dilation of the pupilcauses the patient to have reduced visual acuity for periods of up tohours, until the effect of the dilation chemicals wears off. Dilation ofthe pupil can require a patient to use protective eyewear or to avoidlight of ordinary intensity. Dilation of the pupil can cause a patientdiscomfort. The use of an instrument embodying principles of theinvention can eliminate all of the above negative features of dilationof the pupil.

The inventive technology provides an affordable clinical instrument thatgives the clinician the power and resolution of the SLO, with someoperational features of the most familiar ophthalmic diagnosticinstruments, in an untethered package that is comparable in size andweight to commercial hand-held digital video cameras.

The LSLO can provide stereo fundus images. A binocular LSLO, withlow-cost wearable display technology and more deeply penetratingnear-infrared (NIR) light, can provide real time 3-D morphometricinformation that is usually the domain of slit-lamp biomicroscopes,binocular indirect ophthalmoscopes (BlOs), and stereo fundus photographyat shorter wavelengths. NIR operation increases patient comfort andreduces the risk of phototoxicity during extended exams or procedures.By incorporating additional laser wavelengths as additional channels forparticular wavelength combinations, color information can be capturedand fused with NIR images. The digital LSLO allows the operator toswitch views between live-motion and captured still images with thetouch of a button. Synchronous modulation of laser illumination withline-by-line image acquisition and variable scans allows stereo images,dual-color images, or fluorescence images to be multiplexed andrecorded. The LSLO can be quickly reconfigured for anterior segmentimaging, pupil size and light response. The compact and lightweight LSLOoffers the potential for use as a hand-held emergency care aid,particularly with blood in the vitreous from eye or head trauma. Aportable digital LSLO which performs some of these functions at a costapproaching indirect ophthalmoscopes, while retaining much of theconfocal and NIR advantages of the SLO, becomes more clinicallyversatile and commercially attractive.

In one aspect, the invention relates to a line-scanning laserophthalmoscope (LSLO). The LSLO comprises a light source providing asubstantially point source of light; an optical apparatus and aone-dimensional detector. The optical apparatus comprises an opticalcomponent that accepts the light from the laser and provides a line ofincoming light, at least one optical component that (i) scans a portionof an eye with the incoming line of light in a direction perpendicularto the line, (ii) confocally receives reflected light from theilluminated portion of the eye, and (iii) provides output light in aline focus configuration; and a turning mirror that redirects a selectedone of the incoming light and the reflected light. The one-dimensionaldetector detects the output light and provides an electrical signalresponsive to the output light at each of a plurality of locations alongthe line of output light.

The light source providing a substantially point source of lightcomprises a laser. Alternatively, the light source providing asubstantially point source of light comprises a super-luminescent diode.The optical component that accepts the light from the light source andprovides a line of light comprises one or more lenses. Alternatively,the optical component that accepts the light from the light source andprovides a line of light comprises a holographic optical element.

In one embodiment, the LSLO further comprises a signal analysis modulethat decodes electrical signals from the one-dimensional detector andthat generates an array of data representative of reflected light fromthe illuminated portion of the eye.

In one embodiment, the LSLO further comprises a display module thatdisplays information representative of the array of data generated bythe signal analysis module. The one-dimensional detector is a linear CCDarray or a linear CMOS array in some embodiments. In a preferredembodiment, the laser is an infrared laser. In a more preferredembodiment, the infrared laser operates at a wavelength in the range of700 nm to 950 nm. In a still more preferred embodiment, the infraredlaser operates at a wavelength of substantially 830 nm.

In some embodiments, the optical apparatus of he LSLO further comprisesa scanning mirror that provides a scanned line of light having a scandirection perpendicular to the line of light, one or more lenses thatfocus the scanned line of light on a portion of an eye, one or morelenses that confocally receive reflected light from the illuminatedportion of the eye and provide a line of reflected light, a scanningmirror that redirects the line of reflected light, a pupil stop thatprevents unwanted light from proceeding through the optical apparatus,and an objective lens that focuses the redirected line of reflectedlight onto the one-dimensional detector.

In a preferred embodiment, the scanning mirror that intercepts theredirected line of light and provides a scanned line of light and thescanning mirror that redirects the line of reflected light are the samescanning mirror. In a preferred embodiment, the one or more lenses thatfocus the scanned line of light on a portion of an eye and the one ormore lenses that confocally receive reflected light from the illuminatedportion of the eye are the same one or more lenses. In some embodiments,the pupil stop prevents non-confocally received light from proceedingthrough the optical apparatus.

In still another aspect the invention features a line-scanningophthalmoscope. The line-scanning ophthalmoscope comprises a lightsource providing a substantially point source of light, an opticalapparatus and a one-dimensional detector. The optical apparatus (i)receives light from the light source, (ii) scans a portion of an eyewith the line of light in a direction perpendicular to the line, (iii)confocally receives reflected light from the illuminated portion of theeye, and (iv) provides output light in a line focus configuration. Theone-dimensional detector detects the output light and provides anelectrical signal responsive to the output light at each of a pluralityof locations along the line of output light.

In yet a further aspect, the invention relates to a line-scanning laserophthalmoscope (LSLO). The LSLO comprises a light source providing asubstantially point source of light; an optical apparatus and aone-dimensional detector. The optical apparatus comprises an opticalcomponent that accepts the light from the laser and provides a line ofincoming light, at least one optical component that (i) scans a portionof an eye having an undilated pupil with the incoming line of light in adirection perpendicular to the line, (ii) confocally receives reflectedlight from the illuminated portion of the eye, and (iii) provides outputlight in a line focus configuration, and a turning mirror that redirectsa selected one of the incoming light and the reflected light. Theone-dimensional detector detects the output light and provides anelectrical signal responsive to the output light at each of a pluralityof locations along the line of output light.

In a further aspect, the invention relates to a line-scanning laserophthalmoscope (LSLO). The LSLO comprises a light source providing asubstantially point source of light; an optical apparatus and aone-dimensional detector. The optical apparatus comprises an opticalcomponent that accepts the light from the laser and provides a line ofincoming light, at least one optical component that (i) scans a portionof an eye with the incoming line of light in a direction perpendicularto the line, (ii) confocally receives reflected light from theilluminated portion of the eye, the incoming line of light and thereflected light having monostatic beam geometry, and (iii) providesoutput light in a line focus configuration, and a turning mirror thatredirects a selected one of the incoming light and the reflected light.The one-dimensional detector detects the output light and provides anelectrical signal responsive to the output light at each of a pluralityof locations along the line of output light.

In a further aspect the invention relates to a method of making aoptical measurement of an object. The method includes the steps ofproviding an incoming line of light, scanning a portion of an objectwith the incoming line of light in a direction perpendicular to theline, confocally receiving reflected light from the illuminated portionof the object, providing output light in a line focus configuration fromthe received reflected light, separating the incoming light and theoutput light, detecting the output light, and providing an electricalsignal responsive to the output light at each of a plurality oflocations along the line of output light. In one embodiment, the objectis an eye. In one embodiment, the method further comprises the steps ofdecoding the electrical signal, and generating an array of datarepresentative of reflected light from the illuminated portion of theobject.

In still a further aspect, the invention includes a method of making anophthalmoscopic measurement. The method includes the steps of providingan incoming line of light, scanning a portion of an eye having anundilated pupil with the incoming line of light in a directionperpendicular to the line, confocally receiving reflected light from theilluminated portion of the eye, providing output light in a line focusconfiguration from the received reflected light, separating the incominglight and the output light, detecting the output light, and providing anelectrical signal responsive to the output light at each of a pluralityof locations along the line of output light.

In yet an additional aspect, the invention relates to a method of makingan ophthalmoscopic measurement. The method includes the steps ofproviding an incoming line of light, scanning a portion of an eye withthe incoming line of light in a direction perpendicular to the line, andconfocally receiving reflected light from the illuminated portion of theeye, using a monostatic beam geometry for the incoming line of light andthe reflected light. The method also includes the steps of providingoutput light in a line focus configuration from the received reflectedlight, separating the incoming light and the output light, detecting theoutput light, and providing an electrical signal responsive to theoutput light at each of a plurality of locations along the line ofoutput light.

The foregoing and other objects, aspects, features, and advantages ofthe invention will become more apparent from the following descriptionand from the claims.

BRIEF DESCRIPTION OF THE DRAWINGS

The objects and features of the invention can be better understood withreference to the drawings described below, and the claims. The drawingsare not necessarily to scale, emphasis instead generally being placedupon illustrating the principles of the invention. In the drawings, likenumerals are used to indicate like parts throughout the various views.

FIG. 1 is a schematic diagram showing an embodiment of a line scanningimaging system, according to principles of the invention;

FIG. 2A is a side view of the optical layout of an illustrativeline-scanning laser ophthalmoscope that embodies principles of theinvention;

FIG. 2B is a top view of the optical layout of the illustrativeline-scanning laser ophthalmoscope that is depicted in FIG. 2A;

FIG. 3 is a diagram showing the integrated power falling within a circleof a given radius, according to the prior art;

FIG. 4A illustrates the optical effect of defocusing in a prior art fullfield imaging method;

FIG. 4B shows the optical effect of defocusing in a confocal “flyingspot” system of the prior art;

FIG. 4C illustrates the optical effect of defocusing in a line scanningimaging system such as the LSLO of the invention;

FIGS. 5A and 5B show the standard prior art United States Air Force(U.S.A.F.) resolution target #51 at low and high magnification,respectively;

FIGS. 6A and 6B show prior art target images that appear on the reverseof a United States one dollar bill;

FIG. 7 shows forty degree field LSLO images in the left and right eyesof a human subject, according to principles of the invention;

FIG. 8 shows a standard SLO image of the prior art;

FIG. 9 shows twenty degree field LSLO images in a human subject,according to principles of the invention;

FIG. 10 shows illustrative disc image pairs captured in succession withthe LSLO, according to principles of the invention; and

FIG. 11 is an image that illustrates confocal and anterior segmentimaging, according to principles of the invention.

DETAILED DESCRIPTION

The digital LSLO instrument can be used as a relatively inexpensivemulti-mode screening tool to facilitate rapid, non-mydriatic exams forlarge numbers of patients. In some embodiments of the invention, rapidis to be understood as connoting real time operation. As a portabledevice, the instrument aids in the early detection of AMD, and otherdiseases of the elderly, where no economical early warning methodscurrently exist. The digital LSLO complements existing diagnostics andtele-medicine screening tools for detecting onset of diabeticretinopathy. Many elderly patients may have difficulty in adapting theirposture to the demands of any of the standard instruments. Pediatricexamination has similar constraints. Instead, instruments should adaptto the needs of the patient. The compact and lightweight LSLO may beused as a hand-held primary care and emergency care aid. The LSLOaccording to principles of the invention is advantageously used withoutthe necessity to dilate a pupil of an eye, and employs a monostatic beamgeometry. At sufficiently low cost, simplified versions of the LSLO maybe used by EMTs for head trauma where anomalous bulging of the opticdisk is indicative of elevated intracranial pressure, or with blood inthe vitreous, as well as for stereo examination of the anterior segmentand recording of pupil size and response. High-quality images of injuredocular structures can be captured in a fraction of a second, andtransmitted to a treatment center for diagnosis and advice. Veterinaryapplications include animal certification and identification.

Referring to FIG. 1, an embodiment of a line scanning imaging system isshown in schematic form. FIG. 1 can also be viewed as a schematicdiagram showing the steps of a process, such as a method of use of theimaging system, in which each step is represented by a box in thediagram. A light source 1, which in some embodiments is a laser or asuper-luminescent diode, provides a substantially point source of light.In some embodiments, the light is infrared light. In other embodiments,light within the spectral range from the ultraviolet through theinfrared may be provided. The light is received in a line generator 2and is converted to a line of light. In some embodiments, the linegenerator 2 is one or more lenses, or a holographic optical element. Theline of light from the line generator 2 impinges on a beam conditioner 5that includes a beam separator 3 and a scanning reflector 4. The line oflight interacts with the beam separator 3 and the scanning reflector 4in either of two sequences. In some embodiments, the line of lightinteracts with the beam separator 3 before reaching the scanningreflector 4, for example in an embodiment in which the beam separator isa turning mirror or turning prism that intercepts the line of light asit travels in what will be referred to as the incoming direction, e.g.,the direction of travel toward the object to be examined or imaged. Inother embodiments, the beam separator 3 is a turning mirror or turningprism that receives returning light that has been reflected from theobject to be examined or imaged. In either circumstance, the beamseparator 3 and the scanning reflector 4 are configured to oblige theincoming light and the returning light to follow separate paths,respectively, between the light source and the beam conditioner 5, andbetween the beam conditioner 5 and the linear detector 10 (which will befurther described below). An optical interface 6 such as one or morelenses receives a line of light that scans in a direction perpendicularto the line, and focuses the light on an adjacent object 7 to beexamined.

In the embodiment depicted in FIG. 1, the object 7 is a human eye. Theeye 7 includes a cornea 20, a pupil 22 and a retina 24. The eye 7includes a region referred to generally as a fundus 26, which is theinterior rear wall of the eye 7. In other embodiments, the object 7 tobe examined or imaged is a mammalian eye, or the object 7 is an objectof interest that has optical attributes that are subject to examinationby a scanned line of light. The incoming line of light is scanned acrossa portion of the object 7 such as the fundus 26 of the eye. As is wellunderstood, light that impinges an object can be affected in three ways.The light can pass through the object in transmission, the light can beabsorbed by the object and may also be re-emitted, and the light can bereflected by the object. For an object of interest such as the eye 7,there will be reflections from some regions of the eye 7, including thefront surface of the cornea 20, and the front surface of the fundus 26.Some structures in the eye 7 will absorb and re-emit some of the light,such as layers from the front of the fundus 26 and below the fundus 26.The transmission, absorption/re-emission, and reflection properties ofdifferent portions of the object 7 will in general be a function of thewavelength of the incoming light, and will also depend on the structureand composition of the regions of the object 7.

The light that returns to the line-scanning imaging apparatus from theobject 7 is a light in the form of a line, which is the reflection andor the absorption and re-emission of the incoming line of light. It isalso possible that extraneous light may enter the apparatus, for exampleas a consequence of operating the apparatus in an environment whereambient light is present. The returning light, which for simplicity willbe described as reflected light, is received confocally by the opticalinterface 6. Depending on the configuration of the beam separator 3 andthe scanning reflector 4 in the beam conditioner 5, the returning lightis reflected by the scanning reflector 4 in a synchronous manner withthe scanning of the incoming line of light, so that the reflected lightpasses to the line imaging optics 8. The line imaging optics 8reconfigures the reflected light into a line. The line of reflectedlight passes a confocal linear aperture 9 and impinges on a lineardetector 10. In one embodiment, the beam conditioner 5 is configured toposition the beam separator 3 at the conjugate to the cornea 20, and toposition the scanning reflector 4 at the conjugate to the pupil 22. Inone embodiment, the confocal linear aperture 9 is positioned to beconjugate to the line illumination on the retina 24. The confocal linearaperture 9 can be designed to prevent light that is not confocallyreceived by the apparatus from passing through to the linear detector10. In one embodiment, the linear detector 10 is a linear CCD arraydetector, such as a 1×512 pixel linear array. In another embodiment, thelinear detector 10 is a 1×N linear CMOS array, where N is an integergreater than 1 representing the number of pixels in the array.

The electrical signals generated within the linear detector 10 pass toan electrical signal processor 11, such as an analog-to-digital (A-to-D)converter that converts analog light levels to digital signals. Thesignal processor 11 is connected to a processing apparatus such as acommercially available personal computer that can receive, store, andanalyze the electrical signals in digital form, for example by use of aframe grabber. The A-to-D and the computer are optionally connected toan image/capture/display module 12, which can include any of a computermonitor or video display, a printer, a plotter, a machine-readablestorage medium such as one or more of electronic, magnetic and opticalstorage media (e.g., memory chips, magnetic disks, CD-ROM, DVD), and anenunciator such as a speaker. In one embodiment, the apparatus isportable, and the linear detector 10 and signal processor 11 apparatusare miniaturized and are provided on one or more semiconductor chips. Asis well known in the art, power supplies and motors (which are not shownin FIG. 1) are provided to operate the scanning reflector 4, the lightsource 1, the linear detector 10, and the signal processor 11. The imagecapture/display 12 can in some embodiments be a small viewableelectronic display, such as is found in a portable television, acellular telephone, or a personal digital assistant. In someembodiments, the image capture/display 12 is a remote display, forexample a display situated in the office of a consulting specialist, whoreceives the image via a connection such as telephone, television,internet, 25 satellite transmission, or optical fiber interconnection,and who examines the image and provides an opinion thereon.

Different embodiments of apparatus employing principles of the inventioninclude a compact, portable, affordable multi-function LSLO device forconfocal visible and NIR imaging, including stereoscopic and dualwavelength operation, and digital image capture and transmission. Such adevice is attractive in applications ranging from screening in theelderly to pediatric examination, and from field use or emergency careto veterinary medicine. For example, in field use, high-quality imagesof injured ocular structures can be captured in a fraction of a second,and transmitted to a treatment center for diagnosis and advice.Veterinary applications include animal certification and identification.

In one embodiment, the line of light is produced by a laser as the lightsource 1 operated with a fixed cylindrical optic as the line generator2. The line of light is itself eye-safe for extended periods, even ifthe scanning reflector 4 should fail, because the laser light can neverfocus to a point in any failure mode. In other words, the apparatus isinherently safer than scanning spot systems. The apparatus presentsminimal risk to human subjects without the need for extensive failsafeengineering.

FIG. 2A is a side view of the optical layout of an illustrativeline-scanning laser ophthalmoscope (“LSLO”) that embodies principles ofthe invention. The LSLO is a simple, compact device which scans afocused laser line on the fundus. A laser 202 provides a substantiallypoint source of light. In the embodiment of FIG. 2A, the light isexpanded to a line of light by lenses 204, 206 which are cylindricallenses. Other optical components can be substituted for the cylindricallenses 204, 206 to transform he substantially point source of light intoa line of light. The line of light impinges on the turning prism ormirror 208, and is redirected to the scanning mirror 210. The scanningmirror 210 is caused to move by a drive, such as a galvanometer motordrive known in the art for driving mirrors. The line of light is scannedby the scanning mirror 210 and passes through one or more lenses 212,214, 216 which are positioned and/or adjusted to pass the line of lightthrough a cornea 218 of an eye and through an undilated pupil 220 of theeye so as to impinge as a line focused on a fundus 222 of the eye, whichincludes the retina of the eye.

The reflected light exits the eye through the pupil 220 and the cornea218, passes through the one or more lenses 216, 214, 212, is redirectedby the scanning mirror 210 such that reflected light passes around theturning mirror 208 and passes through the pupil stop 224, reaching andpassing through one or more objective lenses 226. The laser line isimaged by the lenses 216, 214, 212, 226 confocally to a linear CCD array228. In one embodiment, the linear CCD array 228 is a DALSA camera with512 14 μm pixels. A single galvanometer-driven mirror 210 performs thescan transverse to the laser line. The linear CCD readout issynchronized with scan motion and acquired with a frame grabber. Arectangular image of the fundus is thus obtained.

In one embodiment, the 830nm laser diode is connected to the opticalassembly of the LSLO via an FC fiber cable. 830 nm is an advantageouswavelength to use, because the human eye is insensitive to thatwavelength, while infrared detectors having reasonable sensitivity areavailable. Accordingly, there is little or no pupillary reflex to thelight, and little discomfort for the subject of the examination. Otherinfrared wavelengths can also be used to advantage. By comparison, thehuman eye reacts strongly to visible light, with both contraction of thepupil and potentially, discomfort and a reaction involving motion of theeye. In the illustrative instrument, commercially available lenses areemployed. The digital camera is a commercially available DALSA digitalline-scan camera Model CB512, having a linear CCD array 228 (1×512) of14 μm square silicon pixels. The gain in this model is not fullyadjustable. Gain compensation is attained by operation at slower scanrates than would otherwise be possible. Different linear CCD arrays 228with increased gain may be advantageously used.

The DALSA camera body houses a number of low-density circuit cards. Thelinear CCD array itself is quite compact. A focus adjustment for thelaser, and line rotation and displacement adjustments to align the laserline with the linear CCD array are provided with standard Newporttip/tilt mounts, rotary mounts, and slidemounts. The line confocalsystem is quickly aligned and optimized over the length of the array.The ophthalmoscopic lens slide is used solely to correct for a verylarge range of ametropia.

In one embodiment, power and computer cables (not shown) attach to thebottom of the DALSA camera body. In a portable embodiment of the LSLO,the connections are eliminated and on-board batteries and an embeddedcomputer are employed. In one embodiment, the device weighs about 3pounds, and can be lifted and manipulated rather easily.

In one embodiment, the LSLO configuration uses a single-mode fibercoupled 3 mW 830 nm laser 202 with an approximately gaussian profile.The laser is collimated and passed through a fixed cylindrical optic204, 206 having 25 mm focal length. The beam remains collimated on onetransverse axis, but focuses near the pupil conjugate and then rapidlydiverges on the other transverse axis. A 5 mm clear aperture prismmirror 208 turns the beam into the optical train, and also acts as apupil stop 224 for pupil reflection and some scattered light, accordingto the Gullstrand principle. The galvanometer driven mirror 210 nearthis pupil conjugate vertically scans the beam. It has a 14 mm clearaperture. This pupil conjugate is imaged to the eye pupil with thescanning lens 212 (80 mm) and two ophthalmoscope lenses 214, 216, eitherthe Volk Super 66 or the Volk 30D (66 or 30 diopters), all with NIRanti-reflection coatings. The 830 nm-optimized achromat scanning lens212 was selected to produce a near diffraction-limited line at theretinal conjugates with good field flatness. These lenses are largerthan necessary and are chosen merely for convenience, availability andcost.

The pupil magnification at the turning mirror 208 (a pupil conjugate)with the Volk 66 is 5×, and the beam size at the eye entrance pupil 220is 1 mm (2.4× magnification and ˜2 mm pupil for the Volk 30D). Themeasured power at the pupil 220 is less than 2 mW. The eye focuses thebeam to near the diffraction limit in the vertical axis on the retina222, but fans the beam rapidly on the other axis. This reduces the powerdensity at the retina 222, relative to a diffraction-limited spot, by afactor of more than 500, e.g., the aspect ratio of the laser line. Forreflected light, the same magnifications give the corresponding size ofthe scanning mirror aperture at the exit pupil: for the Volk 66, theexit pupil is 3 mm, and for the 30D, as much as 6 mm. In the lattercase, the iris of the eye usually will be the limiting stop. As long asthe pupil is large enough to collect light around the illumination pupilstop, the LSLO will function. The collected de-scanned light is imagedby the objective lens onto the linear CCD array. The lens selected is a40 mm achromat, but is neither optimized at 830 nm, nor AR-coated. Thislens is less critical but will affect in-line resolution to some extent.The use of custom lenses may allow optimization at a selectedwavelength.

FIG. 2B is a top view of the optical layout of the illustrativeline-scanning laser ophthalmoscope that is depicted in FIG. 2A. Both thetop and side view are shown because the cylindrical optic 204, 206requires both tangential and sagittal views to visualize its operation.The side view shows the pupil separation at the small turning prismmirror 208 that allows the illuminating (incoming) beam to pass to theretina 222 while acting as a stop for corneal reflections. In this view,the LSLO is indistinguishable from its point-scanning cousin, the SLO.The top view shows the action of the cylindrical lens 204, 206 whichfocuses at the pupil conjugate and diverges to a tightly focused laserline 230 at the retina 222. The line 230 is scanned on the retina 222 bythe scanning mirror 210 and the reflection is descanned and imaged tothe linear CCD array 228. The LSLO of the present invention preservesadvantages such as rejection of interfering scattered light, andrejection of light scattered from defocused planes above and below thefocal plane, even though an entire line is imaged at once.

Both transverse and longitudinal characteristics of the imaging systemsof the invention should be considered in describing the theoreticalperformance limits of the systems. Diffraction at the focal plane, andscattered light reflected from other defocused planes are analyzed. Thepurely focal plane case, as with a planar target such as a resolutionchart, is to be distinguished from volume targets such as biologicaltissues that reflect light from multiple planes. In the following,“focal plane” is understood to mean a conjugate to the image plane wherethe detector or confocal aperture lies.

One characteristic of an imaging system is its Modulation TransferFunction (MTF) or equivalently its Point Spread Function (PSF). Thesefunctions describe how the image of a point source is broadened in theimage plane. In a diffraction limited system imaging diffusereflections, the PSF is the familiar Airy pattern for reflected lightemerging from the target and filling the collection aperture. Theintegrated power falling within a circle of a given radius is shown inFIG. 3, which is well known in the prior art. In the focal plane case,one can think of the interfering light as contributions from the wingsof the total PSFs, including aberrations, of adjacent illuminatedregions. The farther away these imaged points are from a particularconfocal aperture (or pixel), the weaker their contribution to thebackground light. The total power at any given pixel is the sum of allsuch contributions over the entire illuminated area (ignoringscattering). When used to probe a cavity such as the eye, the SLO isideal and nearly background-free because there are no other illuminatedregions: the “flying spot” is the only light source. The total LSLObackground pixel power is effectively a line integral along a stripthrough the center of the PSF since only a line of illumination is used.As a result of the linear scan, there are contributions from the leftand right of each pixel, but the regions above and below the line aredark. Ordinary CCD imaging however, is a complete surface integral overthe PSF, to the limits of the illuminated area. The limiting contrast isfound from FIG. 3 by reading the percentage of total energy at thecentral pixel's edge, whatever its size may be. The focal image contrastis best for the SLO, and worst for standard fundus imaging. The LSLOlies somewhere in between. The sharper the PSF relative to the pixelsize, the smaller the difference in focal plane performance of the LSLOrelative to that of the SLO.

The contribution of out-of-focus regions above and below the plane offocus need to be considered for the case of a volume scattering medium.A significant performance enhancement can be realized with confocalimaging. Three imaging schemes are illustrated in FIGS. 4A-4C.

FIG. 4A illustrates the optical effect of defocusing in a prior art fullfield imaging method. When the media above or below the focal planescatters light, the use of full field illumination results in a severedefect, as will be explained. In FIG. 4A, uniform light 405 impinges ona focal plane 410. A reflection at a defocused plane 420 at distance Zfrom the focal plane 410 will provide a defocused image 430 comprising alarge blur circle at the detector plane. The behavior of the intensitywith Z is analyzed for three cases, namely full field imaging, “flyingspot” imaging, and line scan imagining.

From optical theory, for unit magnification over Area A with uniformillumination I_(o), where the reflectivity function per unit volume ofmedia is Δ(X,Y,Z), and the imaging system f-number is F, the totalreflected light intensity at the image plane I (X,Y,) is given byequation (1): $\begin{matrix}{{I\left( {X,Y} \right)} \propto {\int_{Z}{\int_{A{(Z)}}\frac{I_{o}{\rho\left( {X,Y,Z} \right)}{\mathbb{d}A}{\mathbb{d}Z}}{\left\lbrack {\left( \frac{Z}{2F} \right)^{2} + \left( {\lambda\quad F} \right)^{2}} \right\rbrack}}}} & (1)\end{matrix}$

The function of Z, obtained by first integrating over the area at each Zplane, is a “range gate” which describes sensitivity to scatter fromregions above or below the focal plane. Actual evaluation of theseintegrals is made rather complex by aperture shape. However, theapproximate dependence of the area integrals on Z can be found byinspection. The intensity of the defocused reflected light at each pixeldrops off as Z⁻². The area producing this illumination on that pixelincreases with Z². This occurs at every layer in the sample. Integratingjust over area, the resulting range gate function is approximatelyconstant, i.e., independent of Z. This means there is no effective rangegate. Every layer in the resulting image is weighted only by itintrinsic reflectivity. Unless the reflectance is strongly confined to aregion very near the focal plane, the image contrast is quicklyoverwhelmed by defocused light.

The MTF can written as a function of spatial frequency (k) as given inequation (2): $\begin{matrix}{{MTF} = \frac{\left\lbrack {{I_{\max}(k)} - {I_{\min}(k)}} \right\rbrack}{\left\lbrack {{I_{\max}(k)} + {I_{\min}(k)} + {2I_{defocus}}} \right\rbrack}} & (2)\end{matrix}$where I_(min)(k) and I_(max)(k) give the ideal focal plane contrast atgiven spatial frequency, and the defocused light intensity shows theeffect of background light on contrast: I_(defocus) increases directlywith Z-thickness in a uniformly scattering medium. Therefore, the fullfield imaging method is unsuitable in scattering media where thethickness of the sample is greater than the depth of field scale (8F²).Contrast is halved when volume-integrated scattering anywhere in theoptical path is equal to the focal plane reflection. This is the sourceof the sensitivity of conventional fundus image contrast to mediaclarity.

FIG. 4B shows the optical effect of defocusing in a confocal “flyingspot” system of the prior art. The equation for the intensity I (X,Y)remains the same except for a modification as a consequence of focusingthe illuminating laser light to a point confocal with the aperture. Thisadds an identical defocus factor in the denominator in equation (1). Therange defocus light falls off as Z⁻⁴, rather than Z⁻². Integrating overarea, the resultant range gate function has dimensions of Z⁻². The fullgate width at half maximum is just the usual definition of the depth offield. This weighting of Δ is integrable in Z, so that uniformscattering from surrounding tissue will not destroy focal plane imagecontrast. The confocal flying spot method of the prior art providesintrinsic sectioning properties, limited only by extinction due toabsorption and scatter.

FIG. 4C illustrates the optical effect of defocusing in a line scanningimaging system such as the LSLO of the invention. For a line scanningsystem, the system focuses the laser light 435 to a line confocal withthe linear detector array 440 by use of optical components 450 In thisconfiguration, the illumination intensity falls off as Z⁻¹. Thedefocused intensity therefore falls off as Z⁻³. Integrating over area,the resultant range gate function has Z⁻¹ dependence, with a gate widthproportional to the depth of field. However, this weighting of Δ is notintegrable in Z. Rather, it has only a weak logarithmic divergence.Uniform scattering from surrounding tissue will reduce focal plane imagecontrast. Nevertheless, a line scanning system provides usefulsectioning properties, because contrast falls off much less rapidly inthick samples, and is far less sensitive to more remote media opacities.

Laser imaging systems generally tend to exhibit speckle patterns, andthis is so for both the SLO and the LSLO. Except near smooth interfaceswith changes in refractive index, biological systems tend to scatterlight from spatially distributed sites, with sizes and separations fromnanometers to microns. Because the laser light is spatially coherent,this means that the phase relationships of the reflections along thebeam (at least within one coherence length) are preserved. The totalintensity of the light collected from such a region is the coherent sumof many contributions. The random walk nature of the amplitude sum leadsto constructive and destructive interference with large variations inpower falling on the aperture or on each pixel, especially if theaperture or the pixel size is near the diffraction limit. Thediffraction limit can be thought of as “one speckle” in the transversedirection. This effect is frequently countered by using a less confocal(larger) aperture collecting light over a larger area which tends toaverage away some speckle. This solution is not available for the LSLO,and LSLO imaging is roughly equivalent to so-called “tightly confocal”SLO imaging. The effective image resolution is roughly halved in thecoherent case.

A significant improvement is realized by using super-luminescent diodeillumination. Current commercial devices with 25 nm bandwidth and ˜10 μmcoherence length are available at low prices, with power levels of a fewmilliwatts. Over the depth of field in the tissue, the speckle willsubstantially average away, producing smoother less granular imageswithout loss of transverse resolution.

The light gathering behavior of a LSLO embodying principles of theinvention is compared to a standard point-scanning system. The modelused for calculation assumes identical optical geometries and detectorquantum efficiencies. Both systems are modeled to scan vertically at theframing rate. For a 500×500 image at 30 Hz framing rate, the horizontalscan rate f_(H), of the SLO is 15 kHz. The “flying spot” detectorrequires a bandwidth of f_(H) times the number of pixels per line,N_(Hpix). To resolve 500 horizontal pixels at 15 kHz, the bandwidth ismore than 10 MHz. This can be achieved because the full power of up to afew milliwatts is focused at the retina confocally with the detectoraperture. The reflected power collected depends upon the incident powerP_(I)(say 1 mW), the local reflectance, R(X,Y), of the retina (less than10% in NIR), and the collection solid angle Ω(˜10⁻³ sr). This amounts toa typical range from about 1 to about 100 nW. The noise-equivalent power(NEP) of the silicon detector is one noise contribution, and another isshot noise. An acceptable signal-to-noise ratio SNR is easily reachedwithin the required bandwidth. The dynamic range of 8-bit imagesrequires a SNR >255 to fully utilize the available range, that is, anoise level less than the signal strength represented by the leastsignificant bit. $\begin{matrix}{{SNR} = \frac{\left\lbrack {\eta\quad{R\left( {X,Y} \right)}\Omega\quad P_{I}} \right\rbrack^{2}}{{{NEP}\left( {f_{H}N_{Hpix}} \right)} + \left( {\eta\quad R\quad\Omega\quad P_{I}E_{v}f_{H}N_{Hpix}} \right)}} & (3)\end{matrix}$where η is the quantum efficiency and E_(v) is the energy per photon atthe illuminating wavelength. The thermal noise of a small siliconphotodetector can be ˜10⁻¹⁵ W/(Hz)^(1/2). Readout noise of a read-outamplifier will usually dominate the NEP for silicon photodetectors.Depending upon collected power, the SNR may be limited by eitherdetector/amplifier noise or shot noise. When dominated by shot noise theSNR becomes $\begin{matrix}{{SNR} = \left\lbrack \frac{\eta\quad R\quad\Omega\quad P_{I}}{E_{v}f_{H}N_{Hpix}} \right\rbrack} & (4)\end{matrix}$

The LSLO images an entire line at once. No transverse scan is required.The readout of the linear CCD array represents a “scan,” but it can beperformed during the time that the line is repositioned. The effectiveintegration time is 1/f_(H), instead of 1/f_(H) N_(Hpix) as for theflying spot system. For the same average power at the retina, the linescanner must spread the beam with a cylindrical optic to form a linecovering all N_(Hpix) at once. In other words, the power at each pixelis reduced in proportion to the number of pixels: P_(I) per pixel forthe SLO becomes P_(I)/N_(Hpix) for the LSLO. Therefore the equation, andthe shot-noise limited SNR, is unchanged and the line scan and flyingspot systems are equivalent as regards SNR. However, because theinstantaneous power per pixel is smaller by N_(Hpix) for the LSLO, whilethe detector/amplifier NEP term only drops by (N_(Hpix))^(1/2), thedetector/amplifier thermal noise contribution is (N_(Hpix))^(1/2) timesgreater. High quality linear CCD arrays/amplifiers are able to operatenear the shot noise level of a few hundred photoelectrons before othernoise sources become important. Excessive noise would appear as snowover the acquired images, over and above the speckle noise. No suchnoise has been observed at the quoted eye-safe light levels.

The model can also be extended to evaluate the full image case of theprior art. For a square CCD array in full field operation, the powerlevel per pixel is reduced still further by another factor ofN_(lines)(≈N_(Hpix)). The detector/amplifier noise is most likely todominate, and CCD imaging becomes noisy at these low eye-safe lightlevels. Flash fundus imaging or higher illumination powers must be used,and all confocal advantages are lost.

The operation of the LSLO has been tested to determine the resolvingpower and diffraction limits of the system, using both biologicalsamples, such as an eye, and inanimate, mechanically produced targets.

The width, w, of the laser line beam at the retina, (to the first nullin the Line Spread Function) is given by:w/2n8f_(eye)/d˜38 microns with the Volk 66, or ˜19 microns with the 30D,for the eye,andw/2 8f_(model)/d˜42 microns with the Volk 66, or ˜21 microns with the30D, for the model eye.In one embodiment, the best focused beam width based on resolutiontargets appears to be somewhat larger. This is attributable in part toaberrations in some non-optimized elements with the optical train, andperhaps to forward scatter from optical surfaces. The pixel sizereferenced to the retina is designed to roughly match these beam widths.For the Volk 66 and 30D, the pixel diagonals at the model retina are 40μm and 20 μm respectively. The horizontal and vertical Nyquist limit istwice the pixel spacing or 56 μm and 28 μm for the two magnifications,or 17 and 35 line pairs per millimeter.

With a fixed 3 mm eye entrance pupil, or ˜7 mm and 14 mm at the pupilconjugate for the Volk 66 and 30D respectively, the Airy diffraction atthe CCD array due to the 40 mm objective is 11.7 μm and 5.8 μm. To firstapproximation, the net double-pass image optical resolution element isthe root-mean-square sum of these contributions, or 58 μm and 29 μm.This closely matches the Nyquist limit of the pixel array.

FIGS. 5A and 5B show the standard United States Air Force (U.S.A.F.)resolution target #51 at low and high magnification, respectively.Because the model eye consists of an achromat in front of the planartarget, ophthalmoscopic lenses overcorrect for field curvature thatwould be present in the eye. The bright central region is due to fieldcurvature moving target plane out of the depth of field at high scanangles. Resolution is determined by reading off the group and linenumber of the smallest resolvable line triplet. Despite some focusirregularities of the Volk 66 lens interacting with the model eyeoptics, the resolutions, judging from the limits of visibility of theU.S.A.F. target triplets, are:

-   -   For low magnification 40 degree field: group 2, line 6,        corresponding to 7 line pairs per mm or 143 μm per line pair    -   For high magnification 20 degree field: group 3, line 6,        corresponding to 14.3 line pairs per mm or 70 μm per line pair.

In each case approximately 5 pixels can be counted between lines at thelimiting resolution. These resolution values are approximately twice thecalculated incoherent values, as expected. The contrast is expected tovanish near the Nyquist limit, and the threshold of visibility forcoherent illumination will always lie somewhat above this limit, usuallya factor of two. The slight translucence of the matte target surfaceitself gave rise to apparent reduction of the contrast having nothing todo with LSLO optics, as well as a highly speckled appearance, which hasan adverse impact on apparent resolution. Denser targets (e.g. imagesthat appear on the reverse of a United States one dollar bill) placeddirectly at the first retinal conjugate (no Volk lens) have an improvedappearance as in FIGS. 6A and 6B. Another interesting effect observed isthe difference in contrast between the horizontal and vertical bars,seen clearly in FIG. 5B. This can be understood as the effect of theproximity of bright pixels to the left and right on the imaged line. Thevertical bars, being only two or three pixels wide have considerablebackground contributions from the neighboring bright regions, whose PSFextends over two pixels. However, on the horizontal dark lines, adjacentpixels on the line are dark except at the ends of the lines, with littleor no consequences for contrast.

The widths of the laser line were w/2 n8f/d˜40 microns with the Volk 66,or ˜20 microns with the 30D. The length of the laser line was set tocover the fields of interest of about 40 degree and 20 degreehorizontal. In order to have minimal variations in brightness along the7 mm CCD array, the FWHM has been scaled via the focal length of thefixed cylindrical lens, to no less than 7 mm at the model retina.Approximately 1 mW of power falls fairly uniformly on the central 7 mmof the line, which is useful for power density calculations in the worstcase (e.g., use of the 30D optic):Length, L˜0.7 cm.

Stationary Line Power Density at the retina 1 mW/(wL) ˜500 mW/cm². Safeexposure times at such power densities at 830 nm is at least 10 seconds,and consistent with the time needed to for the subjects to avert theirgaze, or for the operator to block the incoming light or turn off thelight source in the event of scanner failure.

A plane wave equivalent at the cornea can be estimated by determiningthe power at the cornea which corresponds to this power density on asingle 30×30 micron spot, i.e., one virtual laser element of the line.This is simply {fraction (1/250)}^(th) of the incident power, or lessthan about 4 μW.

When scanned vertically through 0.7 cm to form a square image, the timeaverage power density at the retina drops further to less than {fraction(1/300)}^(th) of this power: Average Power Density of laser line scan(full field 7 mm×7 mm)˜2 mW/cm².

The key safety feature of the LSLO is that even if the vertical scannerfails, no laser interlock is needed because the stationary line itselfis eye-safe over the few seconds required to move the volunteer's eyeaway. The fixed cylindrical optic, which cannot be removed withoutdisassembling the instrument, ensures that the power density at theretina can never be greater that the quoted values.

The LSLO of the invention has been compared with SLOs of the prior artthrough the acquisition of wide field images. Forty degree field LSLOimages in the left and right eyes of a human subject are shown in FIG.7. Sharp images were obtained with the LSLO, and typical characteristicsof confocal infrared image were seen: a dark disc, well-resolved brightvessel lumen, lighter arteries and darker veins, foveal reflex in somesubjects, capillaries and choroidal vessels, and variations inpigmentation. The left eye above shows a retinal scar and some residualfeatures of prior central serous retinopathy. Because of the relativelysmall pupil required for these images and the modest depth of field,clear images can be obtained well into the periphery. For comparison, astandard SLO image of the prior art at slightly higher magnification isshown in FIG. 8.

The capabilities of the LSLO of the invention are demonstrated byrecording macular and disc images. A selection of twenty degree fieldLSLO images in a human subject are shown in FIG. 9. The imagesdistinctly show veins and arteries, retinal nerve fiber foveal reflex,and other morphology.

In some embodiments, the LSLO provides the ability to collect stereopairs. In conventional stereo imaging, the pupil aperture is opticallysplit and two images are captured corresponding to the left and rightfields. The parallax between the images contains the depth information.Depth of field is determined by the numerical apertures of theindividual fields. Because of the finite depth of field of the LSLO withdifferent viewing angles, it is equally effective at gathering depthinformation. But in addition, due to its confocality, defocused lightfrom above and below the plane of focus is suppressed. This allowssuperior 3D visualization of deeper retinal structures.

FIG. 10 shows illustrative disc image pairs captured in succession withthe LSLO, with an approximately 1 to 2 mm lateral shift in pupilposition. This purely lateral pupil shift allowed the same image to becaptured at two viewing angles separated by 3 to 6 degrees and is aneffective simulation of anticipated live-motion, split-pupil aperturebinocular LSLO operation. These images are displayed side-by-side inFIG. 10 at the appropriate separation, so that when viewed from 2 feet(60 cm) or more from the page, the image can be made to fuse in a stereoview.

In FIG. 10, the shapes and orientations of the vessels near the disc areclearly visible. Left/right focus is slightly different due tosuccessive image capture. The perception of a mild fogginess in theimages is due to the low resolution in the images (500×512), andspeckle. High resolution images, and perhaps super luminescent diode(SLD) illumination, should greatly reduce granularity.

FIG. 11 shows a demonstration of confocal and anterior segment imaging.The image of FIG. 11 was obtained when the ophthalmoscopic objective wasremoved and the anterior segment of the subject's eye was placed at theconjugate image plane.

An embodiment of the LSLO of the invention preferably operates at twomagnifications, and is configurable to permit imaging of an anteriorsegment and non-mydriatic imaging of the posterior segment. In oneembodiment, this is accomplished using one of two interchangableophthalmoscopic lenses with rotary focus. In other embodiments, theophthalmoscopic lenses are demountable, and can be interchanged, or theLSLO can be operated without an ophthalmoscopic lens. The LSLO deviceincorporates all necessary electronics and optics for image acquisition,without the need for external image acquisition, a computer or a CRT.The LSLO device provides on-board camera captured image storage andimage downloading.

In some embodiments, the use of two substantially similar instrumentstogether can provide additional functionality. Dual channels can beintegrated that can be configured for multi-wavelength operation andreal time binocular imaging. Wearable micro-display technology permitsthe operator to manipulate the device with an unobstructed visual field,while glancing a few degrees off axis, such as upward or downward, tothe color/stereo (left and right eye) display. The displays appear tomerge near the hand-held device so that minimal accommodation is neededwhile shifting gaze from patient to stereo display. The use of anadjustable facial support system or mask, which makes possible theoperator gently holding the apparatus in place adjacent to the patient,provides all the stability and articulation that the lightweight LSLOneeds for patients in any orientation.

Equivalents

While the invention has been particularly shown and described withreference to specific preferred embodiments, it should be understood bythose skilled in the art that various changes in form and detail may bemade therein without departing from the spirit and scope of theinvention as defined by the appended claims.

1. A line-scanning laser ophthalmoscope, comprising: a light sourceproviding a substantially point source of light; an optical apparatuscomprising: an optical component that accepts the light from the laserand provides a line of incoming light; at least one optical componentthat (i) scans a portion of an eye with the incoming line of light in adirection perpendicular to the line, (ii) confocally receives reflectedlight from the illuminated portion of the eye, and (iii) provides outputlight in a line focus configuration; and a turning mirror that redirectsa selected one of the incoming light and the reflected light; and aone-dimensional detector that detects the output light and provides anelectrical signal responsive to the output light at each of a pluralityof locations along the line of output light.
 2. The line-scanning laserophthalmoscope of claim 1, wherein the light source providing asubstantially point source of light comprises a laser.
 3. Theline-scanning laser ophthalmoscope of claim 1, wherein the light sourceproviding a substantially point source of light comprises asuper-luminescent diode.
 4. The line-scanning laser ophthalmoscope ofclaim 1, wherein the optical component that accepts the light from thelight source and provides a line of light comprises one or more lenses.5. The line-scanning laser ophthalmoscope of claim 1, wherein theoptical component that accepts the light from the light source andprovides a line of light comprises a holographic optical element.
 6. Theline-scanning laser ophthalmoscope of claim 1, further comprising: asignal analysis module that decodes the electrical signal from theone-dimensional detector and that generates an array of datarepresentative of reflected light from the illuminated portion of theeye.
 7. The line-scanning laser ophthalmoscope of claim 6, furthercomprising: a display module that displays information representative ofthe array of data generated by the signal analysis module.
 8. Theline-scanning laser ophthalmoscope of claim 1, wherein theone-dimensional detector is a linear CCD array.
 9. The line-scanninglaser ophthalmoscope of claim 1, wherein the one-dimensional detector isa linear CMOS array.
 10. The line-scanning laser ophthalmoscope of claim1, wherein the laser is an infrared laser.
 11. The line-scanning laserophthalmoscope of claim 10, wherein the infrared laser operates at awavelength in the range of 700 nm to 950 nm.
 12. The line-scanning laserophthalmoscope of claim 11, wherein the infrared laser operates at awavelength of substantially 830 nm. 13-24. (Cancelled).